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The role of normal polarization in far-field subwavelength imaging granted by a dielectric microsphere or microcylinder is revealed. Two hypotheses explaining this imaging are suggested. One of these hypotheses is confirmed by exact numerical simulations. It is an efficient excitation of a set of creeping waves at a curved dielectric interface by a normally polarized dipole. After their emission from the microparticle surface these waves create a diffraction-free imaging beam, and subwavelength imaging becomes possible.

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The general concept of Fano resonance is considered so as to show the possibility of this resonance in space. Using a recently found solution for a Bessel wave beam impinging on a dielectric sphere, we analyze the electromagnetic fields near a microsphere with different optical sizes and permittivity values. We theoretically reveal spatial Fano resonance when a resonant mode of the sphere interferes with an amount of non-resonant modes. This resonance results in a giant jump of the electric field behind the sphere impinged on by the first-order Bessel beam. The local minimum of the electromagnetic field turns out to be noticeably distanced from the rear edge of the microsphere. However, this is a near-field effect, and we prove it. We also show that this effect can be utilized for engineering a submicrometer optical trap with unusual and useful properties.

In this work we report a theoretical study of the lateral resolution granted by a simple glass microcylinder. In this 2D study, we had in mind the 3D analogue—a microsphere whose ability to form a deeply subwavelength and strongly magnified image of submicrometer objects has been known since 2011. Conventionally, the microscope in which such an image is observed is tuned to see the areas behind the microsphere. This corresponds to the location of the virtual source formed by the microsphere at a distance longer than the distance of the real source to the miscroscope. Recently, we theoretically found a new scenario of super-resolution, when the virtual source is formed in the wave beam transmitted through the microsphere. However, in this work we concentrated on the case when the super-resolution is achieved in the impractical imaging system, in which the microscope objective lens is replaced by a microlens located at a distance smaller than the Rayleigh range. The present paper theoretically answers an important question: Which scenario of far-field nanoimaging by a microsphere grants the finest spatial resolution at very large distances? We found that the novel scenario (corresponding to higher refractive indices) promises further enhancement of the resolution.